Tripods are known for simplicity and utility. Three legs provide support and stability for most objects, with the construction of the tripod being dependent, at least in part, on the size of the object being supported. Various improvements have been made to tripods directed to ease of set-up and break-down, which is important for sports and nature photographers, for example, where moving quickly from location to location can yield better photographic opportunities. Thus, certain improvements have been directed to quickly collapsible legs that facilitate rapid set-up and break-down. For such improvements, the legs of the tripods typically comprise nested segments that are tapered wider to narrower from top to bottom so that the legs can be quickly extended and retracted.
Various devices and structures have been developed to secure the nested segments of tripod legs, as disclosed in exemplary U.S. Pat. Nos. 921,335, 880,063, 1,358,402, 1,915,628, 2,542,967, and 5,320,316. As noted above, an objective of these devices and structures is to facilitate extension and retraction of the nested leg segments for rapid deployment of the tripod, quick and easy adjustment of its height, and rapid collapse and retraction. In all of these prior art references, the tripod legs are adjustable to set the vertical height of the object supported by the tripod. These adjustable legs may also be set to accommodate an uneven surface upon which the tripod is set to maintain a desired orientation of the object supported by the tripod.
It is uncommon to find a support comprised of two or more nested sections arranged in moving relation to each other where the sections are intended to impede retraction of the nested sections. One such example is found in U.S. Pat. No. 311,578 of Haskell. This patent discloses a scaffolding having vertical uprights A, and a frame B that is movable up and down on the uprights. The vertical uprights A are generally angled away from each other and are connected at an end by a U-shaped spring that enables the uprights to be moved towards and away from each other and that biases the uprights away from each other. A locking bar F is provided below the frame B so that when the frame B is positioned at a desired height, the locking bar F holds the vertical uprights A apart, with the frame B locking itself in place on the vertical frame A by its own weight. The locking bar F is connected to the frame B so that they move together. Consequently, when the frame B is moved up and down along the vertical upright A to position the height of the frame B, the locking member F moves with it. In addition, upward movement of the frame B and locking bar F causes the vertical uprights A to move apart from each other due to interference with the locking bar F, and downward movement of the frame B causes the vertical uprights A to move towards each other. Thus, the width of the space defined between the vertical uprights A is variable as a function of the position of the frame B and locking bar F. This is necessarily the case for Haskell because its disclosure is directed to a scaffolding having an adjustable height and that is securable at a location once a desired height is set. Thus, Haskell teaches a structure that is positionable by a user at any of a plurality of heights and, once so positioned, secured at that height by interference between and among the various parts of the scaffolding. Thus, the scaffolding of Haskell would not work if the width of the space between the uprights A was fixed because it would be one of wider than, narrower than, or the same as the width of the locking bar F, in which cases the frame B would not be adjustable downward or upward, or securable in place. To perform the essential function of the scaffolding of Haskell—adjustability—the width between the uprights must be adjustable. Finally, as Haskell is directed to a scaffolding, it is essential that the frame B be movable up and down along the vertical uprights A so that the scaffolding can be adjusted to the desired height. It is therefore also essential that the vertical uprights A be movable towards and away from each other as the frame B is moved upward and downward along the uprights. Having vertical uprights A at a fixed distance from each other (i.e., defining a fixed width between them) would render the disclosure of Haskell inoperable for its intended use and purpose of providing a vertically adjustable support for a platform for plasterers, paper hangers, etc.
As noted above, tripods are generally designed to facilitate rapid set-up and breakdown, or to provide locking adjustability. What is lacking in the prior art is a tripod that prevents collapse, which is the problem to which the present invention is directed.